<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Title</title>
</head>
<body>

</body>
<script>
	function averageTime(arr){
		const times = []
		arr.forEach(item => {
			const a = item.split(':')
			const h = parseInt(a[0])
			const m = parseInt(a[1])
			times.push(h * 60 + m)
		})
		const average = Math.floor(times.reduce((acc,num) => acc + num,0) / times.length)
		const h = Math.floor(average / 60)
		const m = average % 60
		return `${h}:${ m < 10 ? '0' + m : m}`
	}
	const arr = ["8:15", "6:35", "11:22"]
	console.log(averageTime(arr))
</script>
</html>